The present invention relates to a foreign object determination device, a foreign object determination method and a foreign object determination program.
Fingerprint authentication is attracting attention as one type of authentication system for identifying individuals. A fingerprint is unique in that it is different for every person, and that it does not change even with the lapse of time. Accordingly, it is said that fingerprint authentication is more reliable than the currently prevalent password authentication or the like. As a method of fingerprint authentication, for example, there is a method of performing fingerprint authentication by a finger mounted on a mounting surface being irradiated with light, and using a ridge-shaped pattern image of the fingerprint obtained by focusing and imaging, via an optical system, the reflected light that scatters due to the unevenness of the fingerprint (refer to Patent Document 1 below).
[Patent Document 1] Japanese Patent Publication No. 3100456
Meanwhile, with the fingerprint authentication described in foregoing Patent Document 1, when a foreign object such as a tape is attached to the fingertip, a proper ridge-shaped pattern image cannot be obtained and the fingerprint authentication cannot be performed appropriately.